1. Technical Field
The present invention relates to braking systems, and methods of retracting a brake pad from a rotor, and more preferably, to a system for and method of retracting a brake pad utilizing active material actuation.
2. Background Art
It is known in the art to engage a brake pad and rotating rotor (or “disk”) to effect a braking force when a body, such as a vehicle, is in motion; and to further cause the retraction of the brake pad when braking force is undesired (e.g., during cruise conditions). Conventionally, mechanical, electro-mechanical, and hydraulic systems have been developed to that end. Of these, one type of conventional system features a hydraulically driven floating caliper/single-piston configuration wherein the pads are not actively retracted from the disk. Instead, a rubber piston seal and/or wobble in the rotor works to pull/push the pads a small distance away from the rotor; however, brake drag (i.e., light contact remaining between the pad and rotor after actuation) is still often experienced. Other conventional systems utilize a seal groove and caliper/pad retraction springs to aid in reducing brake drag but do not completely eliminate the condition.
Of further concern in the art, when the vehicle is in park, these prior art systems typically do not separate the pad from the rotor. This increases the likelihood of corrosion, and as a consequence, thickness variation in the rotor. Thickness variation may, in turn, result in brake pulsation; a nuisance often experienced by drivers. Finally, other concerns in the art involve tradeoffs between pedal travel and caliper hold-off pressure.